Facing the same decision earlier this year (and curiously enough, also already owning a Gryphon) … I went with a Swift in the end, (partly to keep it in the family), but mostly to do with fork / transmission options.
(My specific reason won’t help your decision, but mine is set up with a 135mm front end, in a set of Enablers. At 470mm A-C they work perfectly with the Swift, but would have goosed the Fortitude’s handling somewhat…).
I’ve got a Genesis Latitude, which is a really nice frameset, and I’ve seen plenty of Genesis road bikes, so I’d have no doubt that the Fortitude is similarly well thought out / put together.